Most agricultural tractors and some industrial tractors are provided with a rear mounted power take-off drive which is used to transmit power to an attached implement. Operation of the power take-off drive is controlled by a lever normally mounted on the left-hand side of the steering column. This lever, which extends through the dashboard, is susceptible to being bumped or knocked as the driver enters or exits the tractor cab. The possibility of inadvertently engaging the power take-off (PTO) presents a safety risk especially to another person who may be working on an attached implement, which is connected to the PTO drive, in the belief that the PTO is disengaged.
One method for preventing such engagement is described in U.S. Ser. No. 397,637, filed on July 12, 1982, wherein a roller, which is attached to the lever, is capable of engaging in a recess formed on an arcuate sector which is fixed to a pin. The lever is spring biased to a position such that the roller will engage the recess when the lever is in the disengaged position. Although such a lever has proved to be very successful in overcoming the inadvertent shifting problem, it has been noticed that on rare occasions, the lever is still capable of moving to the engaged position should the roller roll out of the recess. Other disadvantages of the pin lever arrangement are that it is complicated in structure and is rather costly to manufacture and assemble.